Methods and devices to detect stroke in a subject

Abstract

The invention describes a method of determining the presence of acute cerebral ischaemic disorder in a subject comprising: a. measuring the concentration of one or more purines in a body fluid of the subject, the purines being selected from adenosine, inosine, hypoxanthine, xanthine and ATP, and b. comparing the measured concentration with a threshold concentration of the one or more purines, wherein the threshold concentration is preferably in the range 5 μM to 15 μM and wherein a measured concentration higher than the threshold concentration indicates the presence of acute ischaemic disorder. Also is described a method of determining the absence of an acute cerebral disorder in a subject comprising: a. measuring the concentration of one or more purines in a body fluid of the subject, the purines being selected from adenosine, inosine, hypoxanthine, xanthine and ATP, and b. comparing the measured concentration with a threshold concentration of the one or more purines, wherein the threshold concentration is preferably below 4 μM and wherein a measured concentration lower than the threshold concentration indicates the absence of acute cerebral ischaemic disorder.

The invention claimed is: 
     
       1. A method of determining the presence of an acute cerebral ischaemic disorder in a subject, the method comprising:
 a. measuring the concentration of one or more purines in a body fluid of the subject using a biosensor comprising an electrochemical cell, where the purines are selected from the group consisting of adenosine, inosine, hypoxanthine, xanthine, and ATP, and 
 b. comparing the measured concentration with a threshold concentration of the one or more purines, wherein the threshold concentration is in the range from about 5 μM to about 15 μM and wherein a measured concentration higher than the threshold concentration indicates the presence of the acute cerebral ischaemic disorder. 
 
     
     
       2. The method of  claim 1  wherein the acute ischaemic disorder is a stroke, a traumatic head injury, or a transient ischaemic attack (TIA), or a combination thereof. 
     
     
       3. The method of  claim 1  wherein the threshold concentration is in the range from about 5 μM to about 10 μM. 
     
     
       4. The method of  claim 1  wherein the threshold concentration is in the range from about 8 μM to about 15 μM. 
     
     
       5. The method of  claim 1  wherein the measured concentration is the total of the concentrations of two or more single purines each measured individually. 
     
     
       6. The method of  claim 5  wherein one of the purines is adenosine, xanthine, inosine, or ATP, and the threshold concentration is in the range from about 5 μM to about 10 μM; or one of the purines is hypoxanthine, and the threshold concentration is in the range from about 5 μM to about 15 μM. 
     
     
       7. The method of  claim 1  wherein the measured concentration is an equivalent total purine concentration measured by a measurement method responsive to two or more of said purines, and the total purine measurement is calibrated relative to the response of the method to a single calibration purine. 
     
     
       8. The method of  claim 7  wherein the calibration purine is adenosine. 
     
     
       9. The method of  claim 1  wherein the threshold concentration is 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5 or 15.0 μM. 
     
     
       10. The method of  claim 1  wherein the body fluid is whole blood. 
     
     
       11. The method of  claim 1  wherein the purine concentration is measured using a biosensor comprising an electrode having immobilized on the electrode one or more enzymes for which at least one of the said purines is a substrate, and a ruthenium purple mediator. 
     
     
       12. A device configured to carry out the method of  claim 1 , wherein the acute ischaemic disorder is a stroke, a traumatic brain injury, or a transient ischaemic attack (TIA), or a combination thereof, the device comprising a biosensor adapted to measure the concentration of one or more purines in a body fluid, where the purines are selected from the group consisting of adenosine, inosine, hypoxanthine, xanthine, and ATP. 
     
     
       13. The device of  claim 12  wherein the biosensor comprises an enzyme electrode having immobilized on it an enzyme for which at least one of the said purines is a substrate, and a ruthenium purple mediator. 
     
     
       14. The device of  claim 12  wherein the biosensor comprises an enzyme sensor responsive to all four of adenosine, inosine, hypoxanthine, and xanthine. 
     
     
       15. The device of  claim 12  further comprising a controller configured to measure signals from the biosensor and configured to:
 measure a reference signal at a first elapsed time after the biosensor is contacted with a reference liquid, 
 measure a measurement signal at a second elapsed time, optionally substantially the same as the first time, after the biosensor is contacted with a body fluid, and 
 derive the measured concentration of the one or more purines from the said signals. 
 
     
     
       16. The device of  claim 15  wherein the controller is configured to:
 measure a calibration signal at a third elapsed time, optionally substantially the same as the first or the second elapsed time, after the biosensor is contacted with a calibration liquid, and 
 compare the measurement signal with the calibration signal to derive the measured concentration of the one or more purines. 
 
     
     
       17. The device of  claim 15  wherein the said first elapsed time is within the range of 5 seconds to 600 seconds. 
     
     
       18. The device of  claim 12  further comprising a test chamber, where the biosensor is within the test chamber, and wherein the device is configured to introduce a reference liquid or a calibration liquid into the test chamber and to introduce the sample into the test chamber under control of the controller. 
     
     
       19. A method of determining the absence of an acute cerebral disorder in a subject comprising:
 a. measuring the concentration of one or more purines in a body fluid of the subject using a biosensor comprising an electrochemical cell, where the purines are selected from the group consisting of adenosine, inosine, hypoxanthine, xanthine, and ATP, and 
 b. comparing the measured concentration with a threshold concentration of the one or more purines, wherein the threshold concentration is below about 4 μM and wherein a measured concentration lower than the threshold concentration indicates the absence of an acute cerebral ischaemic disorder. 
 
     
     
       20. A method of determining the presence of an acute cerebral ischaemic disorder in a subject, the method comprising:
 measuring the concentration of one or more purines in a body fluid of a subject using a biosensor comprising an electrochemical cell at two or more time points, where the purines are selected from the group consisting of adenosine, inosine, hypoxanthine, xanthine, and ATP, and 
 deriving the rate of change of the measured concentration, and 
 comparing the rate of change with a threshold value for the rate of change, where a rate of change above the threshold rate of change indicates that the acute ischaemic disorder is present. 
 
     
     
       21. A method of determining the presence of an acute cerebral ischaemic disorder in a subject, the method comprising:
 measuring the concentration of one or more purines in a body fluid of the subject using a biosensor comprising an electrochemical cell, where the purines are selected from the group consisting of adenosine, inosine, hypoxanthine, xanthine, and ATP, and 
 measuring the rate of change of the concentration of one or more of said purines, and 
 using the measured concentration and the measured rate of change to determine the presence of the acute ischaemic disorder in the subject. 
 
     
     
       22. The method of  claim 20  wherein the rate of change threshold is in the range from about 2 μM to about 8 μM per hour.